Preparation of chlorodifluoramine



CI-IILORODIFLUORAMINE INFRARED ABSORPTION SPECTRUM OF Feb. 12, 1963 WAVE NUMBERS IN CM E. A. LAWTON ETAL PREPARATION OF CHLORODIFLUORAMINE Filed June 15. 1960 BONVLLIWSNVHJ. .LNEIOH 3d WAVE LENGTH IN MICRONS INVENTORS EMIL A. LAWTON JOHN Q. WEBER ATTORNEY energy oxidizer.

3,6732%??? Patented Feb. l2, 1953 ice 3,077 377 PREPARA'IKGI (3F CHiGRQDlFLUORAMINE Emil A. Lawton, Woodland Hills, and lohn Q. Weber, Topauga, Caiiii, assignors to North American Aviation, Inc.

Filed June 15, 1960, Ser. No. 36,238 9 Claims. (Cl. 2314) This invention relates to a method for the preparation of chlorodifiuoramine. More particularly, this application relates to a method of preparation of chlorodifluoramine with the use of readily available and inexpensive chemicals.

-, Chlorodifluoramine is a compound which is used as a starting com-pound for the preparation of Ni -compounds such as, for example, tetrafluorohydrazine, a very high Chlorodifluoramine is also used in the preparation of other oxidizers and monopropellants. In the prior art, chlorodifiuoramine has been prepared by the reaction of difluoramine with boron trichloride at low temperatures. This constitutes an expensive process be cause of the high cost of the latter chemical and the relatively low yield. Another method for the preparation of chlorodifluoramine is the reaction between difluoramine and carbonyl chloride at a temperature of about 105 C. This reaction is slow and requires a considerable time to obtain an appreciable yield. In a period of about 27 hours, for example, the yield was only about 34 percent, based on the difluoramine used up.

It is, therefore, an object of this invention to provide novel methods for the preparation of chlorodifluoramine. It is also an object of this invention to provide methods for the preparation of chlorodifluoramine which employ readily available and inexpensive chemicals. A further object is to provide processes for the preparation of chlorodifluoramine with relative ease and in good yields. Still other objects will be apparent from the discussion whic' follows.

' The above and other objects of this invention are accomplished by a method for the preparation of chlorodifluoramine comprising contacting (1) dilluoramine with (2) either hydrogen chloride or a combination of hydrogen chloride, water, and chlorine, whereupon (l) and (2) react to produce chlorodifiuoramine. With I-lCl alone, the reaction is believed. to proceed according to the equation The reactants, difluoramine and hydrogen chloride, react upon contact at temperatures ranging from about l42 C. to about 102 C. At -l42 C., the difiuoramine and hydrogen chloride are both solidified. Hence, since mobility of the molecules of the reactants and products is limited in the solid state, no advantage is gained in going to lower temperatures. Temperatures below -l42 C. may be employed if so desired. There is, however, a greater danger of explosion at lower temperatures. At 102 C., the amount of the desired product chlorodifluoramine is'reduced to a minimum with the predominant product being tetraliuorohydrazine. Hence, no purpose is served in carrying out the reaction above about 102 C. Therefore, an embodiment of this invention is the carrying out of the process with anhydrous HCl described hereinabove within the temperature range of from about 142 C. to about 102 C.

I A convenient method of bringing the reactants into reactive contact with each other is to condense the components at suitable low temperatures, as for example, the temperature of -l42 C, and thereafter allowing the components to return to a temperature at which both are in the gaseous phase. Intimate contact between the two reactants is accomplished and high yields of the product chlorodifiuoramine are obtained.

A modification of the process of this: invention is to carry out the reaction in the presence of water with the addition of chlorine and an alkali metal chloride. With water as a diluent, the reaction not only proceeds at a more uniform rate but it is found that it is much more rapid. An added advantage of running the reaction in a water diluent is the increased safety factor since a dilute solution of difiuoramine in water is much less susceptible to explosive decomposition. Another advantage is that the water acts as the complexing agent, therefore no other cornplexing chemical need be added in order to obtain the chlorodifiuoramine product in pure form.

In carrying out the reaction in a water solution, an excess of Water is employed since it serves mainly as a diluent. There is no particularly relation between the concentrations of the hydrogen chloride, the chlorine and the alkali metal chloride that need be observed so long as the concentrations of each are sufficient for the formation of chlorodifiuorarnine upon the addition of difluoramine. For example, good results are obtained when the mol ratio of HCl-to-Cl varies from about 1:5 to about 5:1. The same holds true for the mol ratio of HCl-to-MCI, wherein M represents an alkali metal. The amount of difluoramine added to the solution preferably does not exceed the amount of HCl present in terms of mol units in order to get maximum conversion of the HNF to CINF Therefore, good results are obtained, for example, when the mol ratio of HCl-to-IINF varies from about 10:1 to about 1:1. In order to obviate separation of the product from atmospheric gaseous components or other gaseous contaminants, it is preferred that the reaction be carried out in a closed system from which atmospheric and other gases have been removed. The carrying out of this reaction in a water diluent constitutes a preferred embodiment of this invention.

The following examples will more clearly illustrate the process of this invention. The amounts, where given in parts by volume, are at standard temperature and pressure conditions.

Example I To an evacuated reaction vessel equipped with gas inlet and outlet means, heating and cooling means, and pressure measuring means, were added substantially 22.6 parts by volume of hydrogen clnoride and substantially 29.6 parts by volume of dilluoramine while maintaining the reaction vessel at substantially l42 C. The temerature in this instance was obtained by a methylcyclopentane slush. The reaction vessel and its components were then permitted to warm up to an ambient temperature of 25 C. and maintained at this temperature for a period of substantially 22 hours. During this time a deposit of ammonium chloride was formed on the inside surface of the reaction vessel walls. The volatile reaction product was collected and upon analysis was found to contain 5.3 parts by volume of difiuoramine, 12.7 parts by volume of chlorodifluoramine, together with unreacted hydrogen chloride and SiF the latter coming from reaction with the glass walls of the reaction vessel. This represents a 78 percent yield, based on the amount of difluoramine used up.

To purify the chlorodifluoramine, an excess of dimethyl ether was added to the reaction vessel and the contents thoroughly mixed by shaking in order to form a complex with the hydrogen chloride, SLR, and any unreacted difiuoramine present. Since the boiling point of both the HCl and Sil was close to that of ClNF the mixture containing the complexing agent, complexed components, and the product was then subjected to fractional condensation by passing through successive cold traps maintained at l42 C and 196 C. The ether and complexed materials, as well as any other impurities, were collected at 142 C. and the ClNF product was collected in the trap maintained at 196 C. Chlorodifiuorarnine was collected in substantially 78 percent yield, as stated hereinabove. Chemical analysis of the product shows substantially 40 weight percent chlorine, 44 weight percent fluorine, and 16 weight percent nitrogen, corresponding to the formula ClNF The molecular weight determined by vapor density was 89.5 (calculated 87.5). The infrared spectrum of the product compound is given in the accompanying drawing. This spectrum is identical to that reported in J. Am. Chem. Soc., 82, 2400 (1960). Chloroditluoramine does not decompose at ambient temperatures and can be stored in Pyrex vessels.

Chlorodifiuoramine reacts rapidly with mercury at room temperature to form tetrafluorohydrazine and mercurous chloride.

Example II The procedure of Example I was repeated with the modification that the'reaction Was carried out in the presence of dimethyl ether and the reaction vessel and its contents were permitted toreturn to ambient tem perature. slowly over a period of 8 hours. Thus, the condensed phase. was present over a temperature range of from about 142 C. to about 20 C. The reaction vessel was subsequently cooled and again allowed to warm up. This cycle was repeated 15 times in order to obtain as heavy a deposit of ammonium chloride on the inner surface walls of the reaction vessel as in Example 1. Approximately 4 parts by volume of chlorodifiuoramine was formed and 6 parts by volume of N F was obtained. This represented a yield of substantially 25 percent, based on the amount of difiuoramine used up in the reaction.

Example 111 The procedure of Example I'Was repeated employing substantially 45-.4 parts by volume of difluoramine, HNF and 46.5 parts by volume of hydrogen chloride. The reaction was carried out at a temperature. of substantially 25 C. over a period of substantially 100 hours. Substantially 18 parts by volume of ClNF was formed, together with substantially 1 part N F Unreacted difiuoramine amounting to substantially 5 parts by volume remained in the reaction vessel. The yield was 70 percent of CINF based on the decrease in the HNF Example IV The procedure of Example I was repeated employing 15.6 parts by volume of HNF and 18 parts by volume ofHCl. The reaction was carried out at a temperature of substantially 50 C. for a period of substantially 90 hours. At the end of this time, the gaseous components in the reaction vessel were found to contain substantially 1.5 parts by volume of ClNF and 6 parts by volume of N2 4- Example V The apparatus of Example I was employed in carrying out the reaction in which 14.3 parts by volume HNF and 13.2 parts by volume of HCl were used. The vessel and contents were maintained at a temperature of substantially 102 C. for a period of three hours. The gaseous components at the end of this time contained a trace of CINF and 5 parts by volume of N F Chlorodifiuoramine reacts with amines to produce tetrafluorohydrazine, as shown in the following example.

Example Vl To an evacuated reaction vessel of the type described in Example I were added 6.7 parts by volume of CiNFg and 11.5 parts by volume of dirnethylamine dissolved in 20.8 parts dimethyl ether while maintaining the reaction vessel attemperatures Within the range of --l42 C. to

Example VII The procedure of Example VI was repeated with the modification that diethyl ether was substituted for dimethyl ether and the temperature was maintained at C., or lower, during the reaction period. It was found that the ONE was nearly quantitatively converted t0 N2F4- Example VIII In the apparatus described above, 12.5 parts by volume of dimethylarnine was reacted with 4 parts by volume'of N 1 in the vapor phase at substantially 80 C.- for a period of substantially2 hours. The products upon analysis were found to be methylazide and smaller amounts of diazomethane and azornethane. 1 I

Diazomethane is widely used in chemical syntheses.

Example IX In the apparatus described above, 8 parts by volume of ClNF was reacted with 7 parts by volume of sodium methoxide at ambient temperatures of substantially 25 C. The products, upon analysis, were found to be a white solid consisting of a combination of sodium chloride and sodium fluoride, and NgF Asmall amount of another substance was present.

Example X To the evacuated reaction vessel of Example I was added substantially 0.36 part by weight of difluoramine and 400 parts of water T 0 this was then added substan tially 200 parts of ice water, 1.8 parts of HCl, 3.5 parts of C1 and 2.9 parts NaCl. Effervescence of the liquid in the reaction vessel was immediately observed. The; gaseous components were Withdrawn from the reaction vessel and passed through two cold traps maintained-at 142 C. and C., respectively, and the ChlGI'Q: difluoramine was collected in the receiving vessel mainf tained at 196 C. The amount of product was 0.39 part, equivalent to a 66.7 percent yield, based on the amount of HNF used up.

Example XI The procedure of Example X is repeated, with the modification that KCl is used in place of NaCl and the total amount of water employed is 200 parts and the amount of HCl is 2 parts. The mol ratio of HCl-to-Cl issubstantially 1:5 and the mol ratio of HCl-to-KCI is likewise substantially 1:5. The mol ratio of HCl-to-HNF added is substantially 1:1. A high yield of chlorodifiuoramine is obtained.

Example XII The procedure of Example X is followed, with the modification that RbCl is used in place of NaCl, the amount of water is substantially 1,000 parts and the amount of HCl is substantially 3 parts. The mol ratio of HCl-to-Cl is substantially 5:1 and the mol ratio of HCl-to-RbCl is also substantially 5:1. The mol ratio of HCl-to-HNF added is substantially 10:1. The temperature of the reactants is maintained at substantially 50 C. in this example. A good yield of ClNP is obtained.

The complexing agent used in the illustrative examples hereinabove for removing HCl was an ether, namely dimethyl ether. However, many other Lewis basesare used. The ethers that are employed as complexing agents are hydrocarbon ethers having from 2 to about 12 carsprayer? bon atoms and include alkyl ethers, alkyl-aryl ethers, andsubstituted alkyl ethers, and alkyl-substituted aryl ethers, as well as mixed aryl and alkyl ethers. Also included are cyclic ethers. Non-limiting examples of various ethers are dimethyl ether, diethyl ethers, methyl ethyl ethers, dihexyl ether, methyl phenyl ether, dioxane, etc. Water also serves as a complexing agent.

Although the invention has been described in detail, it is to be clearly understood that the same is by Way of illustration and example only and is not to be taken by way of limitation, the spirit and scope of this invention being limited only by the terms of the appended claims.

We claim:

1. A method for the preparation of chlorodifluoramine comprising contacting (1) difluoramine with (2) hydrogen chloride, whereupon 1) and (2) react to produce chlorodifluoramine.

2. A method for the preparation of chlorodifluoramine comprising contacting (1) difluoramine with (2) hydro gen chloride in the gaseous phase, whereupon 1) and (2) react to produce chlorodifluoramine.

3. A method for the preparation of chlorodifiuoramine comprising contacting 1) difluoramine with (2) hydrogen chloride at temperatures of from about -142 C. to about 102 C., whereupon 1) and (2) react to produce chlorodifluoramine.

4. A method for the preparation of chlorodifiuoramine comprising contacting (1) difiuoramine with (2) hydrogen chloride, whereupon (1) and (2) react to produce chlorodifiuoramine, and adding a complexing agent to form a mixture of chlorodifiuoramine and a complex of hydrogen chloride.

5. The method of claim 4, with the additional step of separating chlorodifiuoramine from said mixture by fractional condensation, and collecting same.

6. The method of claim 4, wherein said complexing agent is a Lewis base.

7. The method of claim 4, wherein said complexing agent is an ether compound having from about 2 to about 12 carbon atoms.

8. A method for the preparation of chlorodifluoramine comprising contacting (l) difiuoramine with (2) hydrogen chloride, whereupon (l) and (2) react to produce chlorodiiluoramine, and adding dimethyl ether as a complexing agent to form a mixture of chlorodifluoramine and an ether complex of hydrogen chloride.

9. The method of claim 8, with the additional step of separating chlorodifluoramine from said mixture by frac tional condensation, and collecting same.

References Cited in the file of this patent Petty: J.A.C.S., vol. 82, pages 2400-1, May 5, 1960.

Luder et 211.: General Chemistry, W. B. Saunders Co., Philadelphia, 1953, pages 208-213.

Topchiev et al.: Boron Fluoride and Its Compounds as Catalysts in Organic Chemistry, Pergamon Press, N.Y., 1959, page 74. 

1. A METHOD FOR THE PREPARATION OF CHLORODIFLUORAMINE COMPRISING CONTACTING (1) DIFLUORAMINE WITH (2) HYDROGEN CHLORIDE, WHEREUPON (1) AND (2) REACT TO PRODUCE CHLORODIFLUORAMINE. 